JPH0413704A - Production of fine particle of crosslinked polymer - Google Patents

Abstract

PURPOSE:To obtain the title spherical fine particles having uniform particle diameters, useful as a filler for coating compound, by subjecting a hydrolyzable silyl group-containing monomer and a comonomer to emulsion polymerization in a water-alcohol solvent, hydrolyzing the silyl group in fine particles of formed polymer and crosslinking. CONSTITUTION:A hydrolyzable silyl group-containing monomer (e.g. p- trimethoxysilylstyrene) alone or a comonomer comprising a mixture of two or more of the monomers and another vinyl monomer (e.g. styrene) copolymerizable with the vinyl monomer alone or a mixture of two or more of the vinyl monomers is subjected to emulsion polymerization in a water-alcohol solvent to give fine particles of polymer, the hydrolyzable silyl group contained in the fine particles of formed polymer is hydrolyzed with an acid or an alkali and crosslinking bond is formed to give the objective fine particles of crosslinked polymer.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing crosslinked polymer fine particles that are particularly useful as media for adsorption or mass exchange treatment, or as fillers for coating materials with good spreadability. .

[Background of the invention]

True spherical polymer fine particles can be used, for example, as raw materials for powder coatings, toners for electronic copying, as fillers for paints and cosmetics that exhibit good spreadability, as fillers for treatments such as adsorption treatment and ion exchange treatment that have high treatment efficiency, or as such fillers. It is currently attracting attention as a useful material for material carriers and fillers for imparting opalescent luster to plastic molded products.

[Conventional technology]

Conventionally, this type of true spherical polymer fine particles has been obtained by a dispersion polymerization method in which monomers are polymerized in a solvent that dissolves the monomers but does not dissolve the copolymer based on the monomers. is known (Y, Almog et al., Polymer Journal Vol. 14, p. 131 (1982))
.

Their method involves dispersion polymerization using a polymer soluble in the solvent together with a quaternary ammonium salt as a dispersion stabilizer to obtain true spherical polymer fine particles with uniform particle size. Furthermore, attempts have been made to obtain true spherical polymer fine particles with uniform particle size by dispersion polymerizing styrene in various solvents using nonionic cellulose derivatives as dispersion stabilizers (C, K .

Ober et al., Journal of Polymer Science.

Vol. 23, p. 103 (1985)).

Furthermore, as another method for producing truly spherical polymer particles, there is a seed polymerization method in which a predetermined monomer is absorbed into the polymer particles using polymer particles as seeds, and then the monomer is polymerized. (Japanese Unexamined Patent Publication No. 61-215602).

[Problem to be solved by the invention]

As mentioned above, the perfectly spherical polymer particles of uniform particle size obtained in this way can be used as fillers for coating materials such as paints and cosmetics, or as fillers for treatments such as adsorption treatment or ion exchange treatment. However, if the polymer fine particles do not have a crosslinked three-dimensional structure, the heat resistance and solvent resistance will be poor, and the range of use will be significantly limited. However, in order to impart a crosslinked three-dimensional structure to the polymer powder, for example divinylbenzene.

When a divinyl compound such as diallyl phthalate is added to a comonomer, the sphericity and uniformity of particle size of the polymer particles decrease.

[Means to solve the problem]

The present invention, as a means for solving the above-mentioned conventional problems,
A copolymer consisting of a vinyl monomer having a hydrolyzable silyl group alone or a mixture of two or more, and another vinyl monomer copolymerizable with the vinyl monomer or a mixture of two or more. monomer.

A crosslinked polymer characterized by emulsion polymerization in a water-alcohol mixed solvent to obtain polymer fine particles, and hydrolyzable silyl groups contained in the polymer fine particles being hydrolyzed with acid or alkali to generate crosslinks. A method for producing coalesced fine particles is provided.

[Vinyl monomer having a hydrolyzable silyl group] In the vinyl monomer having a hydrolyzable silyl group used in the present invention, the hydrolyzable silyl group has the following structure.

(R), -n 5i-Xn In the formula, R is a divalent hydrocarbon group selected from an alkyl group having 1 to 10 carbon atoms, an aryl group, and an aralkyl group, and X is a flucoxyl group such as -OCHa -OC:2 Hs. base, -
It is a hydrolyzable group such as a halogen such as CI or -Br.

Specific examples of the vinyl monomer having a hydrolyzable silyl group include γ-methacryloxypropyltrimethoxysilane, N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane - Hydrochloride, vinyltriacetoxysilane, vinyltrimethoxysilane, etc.

[Vinyl monomer]

Other vinyl monomers copolymerizable with the vinyl monomer having a hydrolyzable silyl group include methyl acrylate,
Ethyl acrylate, n-butyl acrylate, 1so
-Butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, tetrahydrofurfuryl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 1so-butyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, methyl vinyl ether , ethyl vinyl ether, n-
Propyl vinyl ether, iso-butyl vinyl ether, n-butyl vinyl ether, styrene, α-methylstyrene, acrylonitrile, methacrylaterile,
Vinyl monomers such as vinyl acetate, vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, ethylene, propylene, isoprene, chloroprene, butadiene, and also carboxyl groups, hydroxyl groups, methylol groups, amino groups, and acid amide groups. It is also possible to use vinyl monomers having functional groups such as , glycidyl groups, etc. Among vinyl monomers having such functional groups, those having a carboxyl group include acrylic acid, methacrylic acid, itaconic acid, etc., and those having a hydroxyl group include β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, β- Hydroxypropyl acrylate, β-hydroxypropyl methacrylate, allyl alcohol, etc. Those having a methylol group include N-methylol acrylamide, N-methylol methacrylamide, etc. Those having an amino group include dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate. Examples of those having an acid amide group include acrylamide and methacrylamide, and examples of those having a glycidyl group include glycidyl acrylate, glycidyl methacrylate, and glycidyl allyl ether.

The above examples are not intended to limit the invention.

[Comonomer]

A comonomer is obtained by mixing the vinyl monomer having a hydrolyzable silyl group or a mixture of two or more thereof with the other vinyl monomer or a mixture of two or more thereof. The vinyl monomer having a hydrolyzable silyl group is contained in the comonomer in an amount of 0.01 to 30 mol %.

[Polymerization solvent]

As the polymerization solvent used in the present invention, a water-alcohol mixed solvent is used. Alcohols used in the mixed solvent include methanol, ethanol, monohydric alcohols such as 1so-propatool, 5eC-propatool, and t-butanol, polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, and glycerin, and methyl cellosolve. Examples include water-miscible alcohols such as alcohol derivatives such as ethyl cellosolve and cellosolve acetate. The above examples are not intended to limit the invention.

The above water-alcohol mixing ratio is usually 95:5 by weight.
~30 near 0.

[Polymerization initiator]

Examples of the polymerization initiator used in the present invention include water-soluble inorganic initiators such as ammonium persulfate, potassium persulfate, sodium persulfate, and sodium perborate, and 2,2'-azobis(2-methylpropionamidine) dihydrochloride. , 2. A water-soluble organic initiator such as 2'-azobis(2-methyl-N-phenylpropionamidine)dino)hydrochloride, or the above inorganic or organic initiator and sodium sulfite.

Examples include redox initiator systems that use a reducing agent such as sodium bisulfite, sodium hyposulfite, and ascorbic acid. The above examples are not intended to limit the invention.

〔polymerization〕

Polymerization is carried out by mixing the comonomer with the polymerization solvent and heating and stirring the mixture in the presence of the polymerization initiator. In the above polymerization, the concentration of the comonomer in the polymerization solvent is usually about 10 to 40% by weight, and the amount of the polymerization initiator added is usually 0.01 to 5% by weight based on the comonomer. Approximately %. The polymerization temperature is usually about 40 to 80°C,
If desired, polymerization is carried out in an inert gas atmosphere, such as nitrogen gas or argon gas.

In the above polymerization, the comonomer is emulsified in the polymerization solvent and N-polymerized. Through such emulsion polymerization, polymer fine particles having a substantially perfect spherical shape and uniform particle size can be obtained, but in order to hydrolyze the hydrolyzable silyl groups contained in the polymer fine particles to generate crosslinks, polymerization is necessary. Make the system acidic (usually pH 3-6)
Alternatively, the polymer particles are made alkaline (usually pH 7 to 9), or after polymerization, the polymer particles are separated from the polymerization solvent and then brought into contact with an acid solution or an alkaline solution. When an acidic polymerization initiator such as ammonium persulfate, potassium persulfate, sodium persulfate, etc. is used, the polymerization system becomes acidic, so addition of acid is not particularly necessary.

The thus obtained crosslinked polymer fine particles are separated from the polymerization system by well-known solid-liquid separation means such as filtration or centrifugation, and if desired, after separation, they are washed with water, alcohol, etc., and then dried. The thus obtained crosslinked polymer fine particles have a uniform particle size of about 0.1 to 1.0 μm and a substantially true spherical shape.

〔Example〕

Example 1 (Production of Copolymer A) 100 parts by weight of ion-exchanged water and 10 parts by weight of methanol were placed in a reactor equipped with a stirrer, a condenser, a thermometer, and a gas introduction pipe.
0 parts by weight, and further added a comonomer prepared by mixing 4 parts by weight of p-trimethoxysilylstyrene and 16 parts by weight of styrene as a vinyl monomer having a hydrolyzable silyl group, and the rotation speed was 350 rpm. Warm it up while stirring in the oven.6
When the temperature reaches 5°C, 0.2 parts by weight of potassium persulfate is added.

At this point, the pH of the polymerization system was measured and was approximately 5.0 The polymerization system was maintained at 65° C. and reacted for 2 to 4 hours. The pH after 24 hours of reaction was approximately 3°.

After the reaction is completed, the mixture is cooled to room temperature, and the obtained crosslinked polymer particles are collected by centrifugation, washed with water, and then heated and dried at 60° C. for 5 hours. When we randomly selected 100 particles of the obtained crosslinked polymer fine particles using a scanning electron microscope and measured the particle size, the fine particles were perfectly spherical and had an average diameter of 0.3μ.
It has a particle size of

The fine particles were immersed in tetrahydrofuran and toluene and stirred with ultrasonic waves for 1 hour, then separated by f and analyzed in the y solution. As a result, no eluate was found.The state of the particles was again observed using a scanning electron microscope, but the shape and No change was observed in particle size.

Example 2 Comonomers having the same composition were emulsion polymerized in the same manner as in Example 1, but in this example, the pH of the polymerization system was adjusted to about 9 with sodium bicarbonate in advance. The pH was approximately 7 in this example. Analysis similar to Example 1 revealed that the crosslinked polymer fine particles of Example 1 were perfectly spherical and had an average of 0.
．． It had a particle size of 3 μι, and no eluate was present in immersion tests with tetrahydrofuran and toluene.

Example 3 140 parts by weight of ion-exchanged water was added to the same reactor as in Example 1.
Filled with 50 parts by weight of ethanol and 10 parts by weight of ethylene glycol, and further filled with 10 parts by weight of γ-methacryloxyprobyltrimethquine as a vinyl monomer having a hydrolyzable silyl group, 8 parts by weight of styrene, and 2 parts by weight of methyl methacrylate. 1 part of the comonomer was added, and the mixture was heated with stirring at a rotational speed of 350 rpm, and when the temperature reached 75°C, 0.2 parts by weight of potassium persulfate was added. At this point, the pH of the polymerization system was measured and was approximately 6.

The polymerization system is maintained at 65°C and reacted for 24 hours.

The pH after 24 hours of reaction was approximately 3. After the reaction was completed, the same treatment as in Example 1 was carried out, and the particle size of the obtained crosslinked polymer fine particles was measured in the same manner as in Example 1.
The fine particles were perfectly spherical and had an average particle size of 0.4 μm. Further, in the same elution test as in Example 1, no eluate was found.

Comparative Example Emulsion polymerization was carried out in the same reactor as in Example 1 with the same composition and conditions as in Example 1, except that methyl alcohol was removed and 200 parts by weight of ion-exchanged water was used. However, during the polymerization, thixotropic behavior occurred, and a large number of aggregates formed, making stirring difficult.

The particle size of the obtained crosslinked polymer was measured in the same manner as in Example 1, and it was found to be a polymer with a wide particle size distribution.

〔Effect of the invention〕

Therefore, the crosslinked polymer fine particles obtained by the method of the present invention are perfectly spherical and have a uniform particle size, and since they are crosslinked, they have good heat resistance, solvent resistance, etc., and can be used as fillers for paints and cosmetics. It is extremely useful as a processing filler, a filler for plastics, etc.

Claims (1)

[Claims] A copolymer consisting of a vinyl monomer having a hydrolyzable silyl group alone or a mixture of two or more, and another vinyl monomer copolymerizable with the vinyl monomer or a mixture of two or more. A monomer is subjected to emulsion polymerization in a water-alcohol mixed solvent to obtain polymer particles, and a hydrolyzable silyl group contained in the polymer particles is hydrolyzed with an acid or an alkali to form a crosslink. Characteristic method for producing crosslinked polymer fine particles